Hello, does anybody have any experience with jetting a vm24-512 (spigot mount) carburetor on a ct3 175 Yamaha?
I have a freshly rebuilt, ported and polished engine with a bassani pipe. Engine was pressure tested and doesn’t have any air leaks. I’m struggling to find pepper jetting for it. It boggs under wide open throttle currently. I’ve tried 155 to 180 main jets in increments of 5 with very little luck. 
I’ve seen people recommending anything from 140 to 180.
Sudco sent me the carb with 25 pilot and 160 main. I called them and they suggested I run a smaller main, as low as 130. I also talked to some vintage 2 stroke builders that said that I should try something over 200 with this setup. 

Maybe someone can share their setup with this carburetor? What pilot, main and needle you are running?

My pilot is currently a 30 and it seems to like that size. 
I’m in Florida, so no elevation. 

I’d like to get it to at least run on the main jet before I can even do a plug test. 

thank you. 

What air filter do you have?

Brand new uni air filter

Stock air box?  (If a "pod", hopefully without a hard end cap.) 

Also, if you used the super sticky modern filter oil it might not be getting enough air.... 

It’s a pod filter out foam. Not oiled.

How does it run at high rpm and low throttle settings in first gear?  Can you wind it out to redline?

Ignition timing set correctly?  Good spark plug gapped 0.020" to 0.024"?

Did you vacuum test?  Stock CT ignition side crank seal is not dual lip and they can leak under vacuum...  but usually idle would show that.

Other than that, forget "copying"...  you need to give it what it needs.  Mikuni Tuning manual is in Tech Library or online.  One trick is to quickly go from full to 3/4 throttle under load and see what happens.  If it speeds up as you close throttle, main is lean. 

You also haven't mentioned needle jet and needle sizes.  Very important.  They might not flow enough.  Carb is a system with parts that need to work together. 

Is it an old Bassany pipe that the muffler on the end is falling apart collapsing in & stifling it.or tail pipe needs a burn out. In theory the motor should be a rocket 

Does anything change if you run it without the air boot so nothing getting in the way as in restrictions. Videos of good length are great with good audio. Not easy to do I realize but could have us thinking along a different line. Videos must be linked via YouTube or similar. Best of luck & with MarkT on the job I'm sure you'll get it sorted.

I shoulda left it there & gone to bed but thought i'd google one of those carbs just to be sure it doesn't have the side mounted main jet like original CT3--thinking the miniature Oring leak but Ok doesn't apply in this case.
BUT, in this link when googling i see a warning about needle jets--[emultion tube] & needles etc.
Have a read down where says warning.
I didn't get far into it but though might not be relevant but i dunno.
mikunioz.com/shop/vm24-512-24mm-vm-carburetor/?v=c97b334ffd41
Ps, i run a 28 on my AT1 now sporting a reed 175 top end.
Well--was meant to be a 28 but was a cheapy chinese underbored semi-finished one but goes like the wind.
No idea on main jet now but ill look next time i have it apart.
I adapted a mikuni main jet to fit the thread as was way over-rich initialy.
I could show a video but you wouldn't be able to unsee it--it's Ugly & rough haha.

Thanks for replies and help! Also interesting info about the needle and needle jet. Looks like vm28 doesn’t have the same issue.
I decided to order some cheap jets on Amazon despite the warnings about them being machined with lower tolerances. For testing this is a lot cheaper than buying a handful of jets at jetsrus. Out of the jets that I got some of them had messed up threads so just a warning to people that decide to buy those. I ended up with a 230 main and it’s running pretty good so far. I wanted to try a 235 that came with a kit but it has a messed up thread on it. I’ll end up buying 230, 235 and 240 from jetsrus and see if I can go any richer. I’ll do a plug check on it too. But so far the consensus is that 230-240 might be the right jetting on this carb for my motor.

Hopefully this thread helps someone in the future as well.

I’ll post an update when I settle on the main jet after further testing.